Methanol wastewater

First, clarify: 1. How much water is there? 2. What is the methanol concentration in water? 3. If the water volume is low and the concentration is not high, recycling holds little significance; mainly because of the low economic value, making it not worth the effort. 4. If there is a value in recycling, reverse osmosis recycling can be considered.

Can reverse osmosis recover methanol? I’m a bit skeptical; osmotic vaporization or membrane distillation might be possible, but since methanol is the solvent, reverse osmosis can’t retain it either, right?

Take a look at this post on how to handle methanol-containing wastewater: http://bbs.hcbbs.com/thread-69424-1-1.html

Example of High-Temperature Steam Stripping and Incineration Treatment for Methanol Wastewater I. Project Background The industrial wastewater treatment plant of the Methanol Branch of Daqing Oilfield Chemical Co., Ltd. was built in 1990 as a supporting facility for the original 60,000 tons/year methanol production unit; its designed treatment capacity was 120 tons per day. In 1992, the system was upgraded and expanded, increasing its treatment capacity to 200 t/d (COD < 10,000 mg/L). The wastewater treatment process employs the methylotroph biochemical treatment method developed by Shanghai Normal University; after treatment, the quality parameters of the discharged water are such that COD is less than 150 mg/L. As the company continued to develop, a new methanol production facility with an annual capacity of 100,000 tons was put into operation in 1998. In 2000, the existing methanol facility with an annual capacity of 60,000 tons was expanded to 100,000 tons per year. Although both of these 100,000 tons per year methanol production units employ relatively advanced manufacturing processes, and the COD level in their methanol wastewater is lower than that in the original 60,000 tons per year methanol unit, the increased total flow rate of wastewater to 16 m3/hour, along with COD levels that often fluctuate between 2,000 mg/L and 7,000 mg/L, places a huge strain on the wastewater treatment facility. Since September 2005, the problem of wastewater from the treatment plant exceeding regulatory standards has become increasingly severe, posing a bottleneck in helping the branch meet environmental regulations. After analysis, the reasons for this phenomenon are as follows: First, the total amount of water inflowing exceeds the design value, which reduces the retention time of wastewater within the facility ； Secondly, at the end of their service life, the two methanol production units generate more by-products; it is difficult to remove the higher alcohols, hydrocarbons, and impurities present in the residual liquid ； Third, the flotation effect in the air flotation tank of the wastewater treatment plant is poor ； Fourth, the original 200m3 two-stage aeration tank was in disuse after 2000 due to leaks, which reduced the retention time of wastewater within the facility ； Fifth, the dosing is discontinuous, resulting in poor controllability of the dosage. Considering the quality of the methanol industrial wastewater produced by this company and the existing equipment at its subsidiaries, it is theoretically feasible to pre-treat such wastewater using a stripping + incineration method; other methods basically do not meet the required conditions. http://www.iwatertech.com/u/1752/image/weiu02/0---1231--04.jpg Basic process conditions: Crude methanol serves as the raw material in the methanol distillation process. The main components of crude methanol produced from natural gas are as follows (taking a plant with an annual production capacity of 100,000 tons of methanol as an example; synthesis conditions involve pressures below 5 Mpa and temperatures below 290°C, using copper-zinc catalysts): http://www.iwatertech.com/u/1752/image/weiu02/0---1231--05.jpg The methanol production facility is a plant that was upgraded in 2001 to achieve an annual production capacity of 100,000 tons of methanol. Initially, it was designed to send methanol wastewater to a stripping tower for treatment, after which it would be sent back to the demineralization unit for further processing before being used as demineralized water. However, practical experience has shown that the high-carbon alcohols present in the methanol wastewater cannot be completely decomposed under the conditions of the stripping tower, which leads to carbon deposition on the conversion catalysts located in the upper part of the conversion furnace. This has a negative impact on these catalysts over time. As a result, this process has never been put into use, and the methanol wastewater is instead sent directly to the wastewater treatment plant for treatment before being discharged. Since the No. 1 unit is equipped with stripping facilities, it meets the primary requirement for using stripping technology. The conversion furnace is the key equipment in our conversion process and remains in operation continuously; moreover, both the furnace temperature and residual oxygen levels meet the conditions necessary for treating wastewater by incineration. Therefore, from the perspective of the basic equipment requirements, the \"stripping + incineration\" treatment method is feasible. By comparing the data in Tables 3-1 and 3-2, it can be seen that the contents of isobutanol and n-butanol in the crude methanol from a methanol plant are higher than those stated in the available literature. http://www.iwatertech.com/u/1752/image/weiu02/0---1231--06.jpg In April 2006, we carried out this technical modification: we altered the original process for treating methanol distillation wastewater by directing it to a methanol stripping tower. While maintaining the balance of the steam system in the methanol production unit, some superheated steam was fed into the stripping tower to carry out the stripping process on the residual liquid. The vapor produced was sent to the radiation section of the conversion furnace for combustion, while the liquid waste at the bottom of the tower was sent to a wastewater treatment plant for further processing. Regular monitoring was conducted to track changes in the concentrations of key pollutants at the inlet and outlet of the stripping tower. After the modification process was put into use, in order to determine the appropriate operating parameters for the stripping tower, we decided to adopt a step-by-step testing approach. Initially, tests were conducted under operating conditions of a temperature of 150°C and an operating pressure of 0.54 Mpa; thereafter, these two parameters were adjusted and optimized based on the results of sampling analyses, until appropriate operating conditions were finally established. 1. Investment for this renovation: two pumps with a capacity of 10 m3/h and a head of 100 meters (utilizing the existing equipment foundations and power supply); 300 meters of 20#φ50 seamless steel pipes; 5 DN50 valves, 20 DN50 elbows, and 10 DN50 flanges (including insulation). Taking advantage of the high temperature and residual oxygen conditions in the converter, no additional combustion facilities are required. The total investment amounts to approximately 40,000 yuan. The detailed renovation process and changes are shown in the attached diagram. http://www.iwatertech.com/u/1752/image/weiu02/0---1231--07.jpg 2. Material consumption: Steam: (2.5 Mpa, 370°C), 1.5 t/h 3. Operating parameters: P = 0.36 Mpa, T = 140°C 4. Actual operating results: This methanol wastewater pretreatment process has been in use since late April 2006, and it has performed well. In particular, during the maintenance period of the wastewater treatment plant in May 2006, this process played an even more important role; the wastewater treated by the stripping tower met the standards for discharge into the environment. The details are shown in the table below. http://www.iwatertech.com/u/1752/image/weiu02/0---1231--08.jpg As can be seen from the table above, after the modifications, the concentrations of the main pollutants in the wastewater entering the treatment plant remained at a relatively stable low level. The severe fluctuations and high-concentration spikes that used to occur have completely disappeared, ensuring the proper operation of the wastewater treatment system and its effective performance. This has played a crucial role in maintaining the quality of the wastewater discharged by our company, contributing to environmental protection in the region. Conclusion: This renovation extended the sewage treatment process, improved the buffering and shock resistance of the sewage treatment equipment, and significantly increased the rate of sewage discharge meeting standards. The successful implementation of this renovation has broken away from the traditional wastewater treatment methods used in the methanol industry, allowing people to appreciate from a new perspective the wide range of applications for wastewater treatment technologies. It is worth drawing on by methanol manufacturing enterprises or those that generate low-concentration organic industrial wastewater.

The amount of process wastewater generated in methanol production is not large, so it can be fully sent for biological treatment (which is available in such plants).

Methanol is highly toxic; it can accumulate in the human body and have harmful effects. Consuming 10 mL of it can cause blindness, while 30 mL can lead to death from poisoning. To treat methanol wastewater, physical-chemical methods, chemical methods, biochemical methods, and others have been developed and adopted in China; these methods can treat methanol wastewater to varying degrees. Such as venturi extraction, pelargonium pseudomonas treatment, and pure oxygen biological fluidized bed treatment. Physical and chemical treatment methods are incomplete; wastewater containing high concentrations of methanol must be sent to a sewage treatment plant for further treatment before it can be discharged in compliance with standards. Methanol wastewater recovery devices: Biological treatment methods include aerobic biological treatment and anaerobic biological treatment. The aerobic method is commonly used for treating methanol wastewater with moderate to low concentrations; it has a relatively weak capacity to handle shock loads, and improper operation can lead to sludge bulking ； UASB systems are commonly used in anaerobic biological treatment, as they possess excellent capacity for degrading wastewater containing high concentrations of methanol. However, due to the large fluctuations in the quality and volume of such wastewater, single-stage anaerobic digestion processes are prone to acidification under high load conditions, which affects their treatment efficiency and operational stability. To improve the capacity for treating high-concentration methanol wastewater, it is necessary to develop new treatment processes that are highly technologically advanced, cost-effective, and easy to control, through both theoretical research and practical applications.

Generally, methanol wastewater has a high COD value and is biodegradable; if its volume is not large, it can be added to other wastewater treatment systems as a substance to adjust the C:N:P ratio. It’s not clear what the methanol content is, and it’s unknown whether there is any value in recycling it.